Methods and apparatus for straightening or blending elongated workpieces

ABSTRACT

A method of straightening an elongated workpiece, in which the workpiece is supported at two spaced points and straightening forces are applied between these points by an automatically controlled hydraulic ram, governed by a programming system which causes the first stroke of the ram to defect the work beyond the desired final shape by a distance approximately equal to the calculated maximum elastic deformation, the load is then removed and the residual error sensed, and a further series of strokes applied at constant increments, the residual error being sensed between strokes and used to initiate a second series of stroke increments of smaller value until the residual error falls below a final preselected value at which acceptable straightness has been achieved.

United States Patent n91 Galdabini Jan. 30, 1973 [54] METHODS ANDAPPARATUS FOR STRAIGHTENING OR BENDING ELONGATED WORKPIECES [76]Inventor: Renzo Galdabini, l Gallarate,

Varese, Italy [22] Filed: Sept. 7,1971

[2]] Appl. No.: 178,190

[30] Foreign Application Priority Data Nov. 6, [970 Italy ..3l427 A/70[52] US. Cl. ..72/10, 72/30, 72/389, 72/702 [SI] Int. Cl. ..B2ld 7/12[58] Field of Search ..72/10, ll, 12,7, 380, 389, 72/702, 30

[56] References Cited UNITED STATES PATENTS 3,459,018 8/1969 Miller..72/l4 3,48l.l70 l2/l969 Galdahini ..72/ll Primary Examiner- Lowell ALarson Attorney-William D. Hall et al.

57 ABSTRACT A method of straightening an elongated workpiece, in whichthe workpiece is supportedv at two spaced points and straighteningforces are applied between these points by an automatically controlledhydraulic ram, governed by a programming system which causes the firststroke of the ram to defect the work beyond the desired final shape by adistance approximately equal to the calculated maximum elasticdeformation, the load is then removed and the residual error sensed, anda further series of strokes applied at constant increments, the residualerror being sensed between strokes and used to initiate a second seriesof stroke increments of smaller value until the residual error fallsbelow a final preselected value at which acceptable straightness hasbeen achieved.

A 6 Claims, 3 Drawing Figures PATENIEBmao 1915 saw 1 or 3' INVENTOR RNzo GMBABN mzminmsoms 3,713,312

SHEET 2 [1F 3 I INVENTO R RENZQ GALDAE PATENTEDJM so an SHEEI 3 BF 3INVENTOR Rerqzo GA MEN METHODS AND APPARATUS FOR STRAIGHTENING ORBLENDING ELONGATED WORKPIECES This invention relates to processes andapparatus for carrying out straightening operations on elongatedworkpieces such as shafts or spindles. The term straightening as usedherein is primarily intended to refer to a conventional straighteningoperation in which a workpiece is initially out of true straightness andis required to be returned or brought into a truly straight shape. Theterm is however also intended to include corrective bending operationson a workpiece, designed to impart a desired shape thereto, even whenthe final shape is not in fact straight.

The invention may be viewed as an improvement in or modification of theinvention described in U.S. Pat. No. 3,481,170.

In the process described in the said patent a workpiece is straightenedby a series of operations which includes a first straightening strokearranged to impart to the workpiece a deformation beyond the desiredfinal shape, this deformation being approximately equal to, or slightlygreater than, the estimated maximum elastic deformation, the workpieceis then unloaded and the remaining error between its relaxed positionand its desired final shape is then measured or sensed, after which atleast one further straightening stroke is applied to impart adeformation beyond the final shape equal to the sum of the saidestimated maximum elastic deformation and the sensed error remainingafter the first stroke.

The maximum elastic deformation referred to above may be defined as themaximum deflection that can be imparted to the workpiece without anypart of it entering into the plastic range. It will be understood thatin the case of a bar the outer portions of the bar will be subjected toa higher stress and deformation when a bending strain is applied, thenthe inner portions, and the outer portions will therefore reach theelastic limit sooner, i.e. at a smaller total deflection of the bar. Themaximum elastic deformation is reached when any part of the workpiecestarts to enter into the plastic range.

In the straightening process described and claimed in the said U.S. Pat.No. 3,481,170, the value of each of the straightening strokes isdependent upon the residual errorsensed after the previous stroke and isautomatically adjusted by a control device having an input from an errorsensing device which measures the residual error of the relaxedworkpiece after each straightening stroke. in practice it is found thatthis process, though highly effective, requires somewhat elaboratecontrol systems, and it is an object of the present'invention to providea simplified process and apparatus, operating on the same basicprinciples, and capable of achieving substantially equivalent resultsbut with less complicated control stages and control equipment.

Broadly stated from one aspect, the invention consists in a method ofstraightening or applying controlled bending to an elongated workpiece,in which the workpiece is subjected to a bending stroke, which impartsto it a deformation beyond the desired final shape, this deformation (asmeasured beyond the desired final shape) being approximately equal to,or slightly greater than the estimated maximum elastic deformation, and

the workpiece is then unloaded and subjected to a series of bendingstrokes which impart progressively increasing deformation to theworkpiece on a preselected programme of increments and the residualerror between the actual and desired shapes is sensed when the workpieceis unloadedbetween at least some of said strokes, and when the residualerror falls below a first preselected value the workpiece is subjectedto a further series of increasing strokes of smaller progressiveincrements, according to another preselected programme, and the residualerror is again sensed when the workpiece is unloaded between strokes,and when the residual error falls below a second preselected value, theoperation is terminated.

According to a preferred feature of the invention the first series ofstrokes are of progressively increasing length, the increments being ofconstant value, and the second series of strokes are also ofprogressively increasing length, with constant increments of smallervalue than the increments of the first series.

Conveniently the residual error is sensed after each stroke, though insome cases it may be sufficient to sense the error only after apreselected number of strokes.

The method may be applied in practice to a workpiece in a number ofdifferent ways, with the workpiece supported in various differentfashions but the invention is particularly applicable to a method inwhich the workpiece is supported on two spaced supports, and the bendingstrokes are applied to the workpiece between the supports by afluid-operated ram.

According to another preferred feature of the invention the length ofeach stroke is determined by an automatic control system having an inputfrom an error senser arranged to sense the residual error when theworkpiece is unloaded, and an output connected to a ram for applying thebending or straightening strokes, so as to control the length thereof,the control system including a programming section arranged to apply oneor two preselected programmes of increments to the output signal,depending upon whether the sensed residual error is above or below thefirst preselected value.

The invention also'consists in an apparatus for performing the method ofany of the preceding claims including an automatic control systemassociated with an error senser and a fluid operated ram for applyingstraightening strokes to a workpiece supported between two supportpoints, the output from the control system being operatively associatedwith the fluid operated ram so as to control the lengthof the strokes,and the control system including a programming section arranged to applyone of two preselected programmes of increments to the output signal tothe ram, depending upon whether the sensed residual error occurring atthe input is above or below a first preselected value.

The invention may be performed in various ways and one embodiment withcertain possible modifications will now be described by way of examplewith reference to the accompanying drawings, in which:

FIG. 1 is a load deflection diagram illustrating very diagrammaticallyand on an exaggerated scale the successive stages of a straighteningoperation according to the invention,

FIG. 2 is another diagram illustrating the physical straighteningstrokes or stages shown in the diagram of FIG. 1, and likewise on anexaggerated scale, and

FIG. 3 is a block diagram illustrating the main components of astraightening apparatus according to the invention.

Referring first to FIGS. 1 and 2 the workpiece in this example is ametal bar which has initially been bent or deformed, or otherwisedeparts from true straightness as shown in FIG. 2, and is placed over apair of spaced supports 11,12 with its curvature upwards so that thecenter of the barlies at point A immediately below a hydraulicallyoperated straightening ram 13. The final required straight shape of thebar is shown by the straight line 14 extending between the two supports11,12 and the corresponding position of the center of the bar is shownby the origin 0.

In performing the straightening operation it is first necessary tocalculate the maximum elastic deformation of the bar. This can be donewithout great difficulty and to reasonable accuracy, from a knowledge ofthe dimensions of the bar and its material. In the load deflectiondiagram of FIG. 1 the maximum elastic deformation Fp corresponds to theposition P on the curve where the line of the curve begins to deviatefrom a straight line of constant gradient (the value Fp being measuredfrom the original position A).

Having calculated this value Fp a first downward straightening stroke S,is applied to the bar by means of the ram 13 so as to deform the barbeyond the desired final position 0 to an extent beyond the origin 0approximately equal to, or possibly slightly greater than, thisestimated value Fp. With the bar deflected by this first straighteningstroke S, the equivalent point on the load deflection curve is shown atO in FIG. 1. The load on the bar is then removed by withdrawing the ram13 upwards and the position of the point at the center of the barreturns to a new relaxed position R along the line Q R (parallel withAP).

An automatic sensing device (see FIG. 3) then measures the distancebetween this relaxed position R and the origin 0 and provides an outputproportional to this residual measured error E If this residual error E,is greater than a first preselected error value E the process continueswith a second stroke S which exceeds the first stroke S, by an incrementa. The corresponding position on the load deflection diagram is shown atQ and when the load is again removed the central point of the barreturns to position R along the line Q 11 The residual error is againsensed and since in this case the error is again larger than the firstselected value E a further downward straightening stroke is applied toposition S the added increment between S; and S being equal to theprevious increment a. When the load is again removed the central pointon the bar returns along the line 0 R, and again the residual error issensed. At this stage the residual error is found to be smaller than thefirst preselected value E and accordingly the next stage. of thestraightening programme is started. The next stroke S is accordinglytaken down to a position where the added increment b between 8:, and Sis somewhat less than the constant increment a of the first series ofstrokes. From the corresponding position Q on the load deflectiondiagram the central point of the bar returns to position R when the loadis relaxed, and since this value is still greater than the secondpreselected error value E; a further downward straightening stroke S isapplied with the added increment b the same as in the previous stroke.When the load is removed the central point of the bar then returns alongthe line Q R and the sensed error is again found to be slightly greaterthan the second preselected value E A further straightening stroke S istherefore applied with the same added increment b and on relieving theload it is found that the relaxed position of the bar at R is less thanthe second error value E and accordingly the process is then terminatedand the bar is removed from the apparatus since it now lies within thepreselected final straightness limits.

In a possible modification, instead of maintaining constant increments ain the first stage of the programme and constant increments b in thesecond stage, the increments a of the first stage may be variedprogressively; for example they may be progressively reduced in sizetowards the end of this stage, according to the pre-arranged programme.Likewise the increments b in the second stage may be progressivelyreduced. It is however important that the increments b of the secondstage should be smaller than those of the first stage. It will also beunderstood that more than two stages may be used in the straighteningprogramme if required, and if a third or additional stage is employedthe value of the increments in each further stage will be smaller thanthose in the previous stage, and the change from one stage to the nextwill take place when the sensed residual error falls below a particularselected value.

A suitable apparatus for controlling the straightening process isillustrated diagrammatically in FIG. 3. In this apparatus thestraightening ram 13 is powered by an electro-hydraulic power controlunit 22 and the apparatus includes a positional pick-up or error senser16 and an electronic control device indicated generally by 17, includinga computer with a digital memory 18, a programmer 19, a summing device20, a differentiator 21, a control amplifier 23, and an external controlpanel 24.

After feeding from the control panel 24 to the programmer 19 theestimated maximum elastic deformation Fp, the two increments a and b,and the first and .second preselected errors E and E a button is pressedon the panel 24 and an electric signal is generated for beginning thestraightening operation by operating the ram 13. The positional pick-upor error senser 16 produces two signals one of which represents thetotal deflection applied by the ram, and is transmitted to the amplifer23, whilst the other, representing the residual error e, after the loadhas been relieved, is transmitted to the memory of the computer l8. Thiserror signal (e is also compared with the first preselected error signalE, by the differentiator 21 and as long as the residual error e, islarger than the preselected value E an output signal is transmitted from21 to the amplifier 23 to cause the ram to be energized again, theextent of its movement being governed This procedure and apparatusenable a workpiece to be straightened, or brought to a predeterminedshape, in a very economical process involving only a small number ofstraightening strokes and without the complications imposed bycontrolling the added increment of each stroke in accordance with thesensed residual error after the previous stroke.

It will be appreciated that when straightening operations are applied toa group of similar manufactured workpieces such as shafts, all areapproximately of the same dimensions and materials and characteristics,and the value of the increments a and b in the first and second stagesof the programme can be selected by experience to produce the bestpossible results in the shortest possible time.

Iclaim:

1. A method of straightening or applying controlled bending to anelongated workpiece, in which the workpiece is subjected to a bendingstroke which imparts to it a deformation beyond the desired final shape,this deformation as measured beyond the desired final shape beingapproximately equal to, or slightly greater than, the estimated maximumelastic deformation, and the workpiece is then unloaded and subjected toa'series of bending strokes which impart progressively increasingdeformation according to a preselected programme to the workpiece, andthe residual error between the actual and desired shapes is sensed whenthe workpiece is unloaded between at least some of said strokes, andwhen the residual error falls below a first preselected value theworkpiece is subjected to a further series of strokes of smallerprogressive increments, according to another preselected program, andthe residual error is again sensed when the workpiece is unloadedbetween strokes, and when the final residual error falls below a secondpreselected value, the operation is terminated.

2. A method according to claim 1, in which the first series of strokesare of progressively increasing length, the increments being of constantvalue, and the second series of strokes are also of progressivelyincreasing length, with constant increments of smaller. value than theincrements of the first series.

3. A method according to claim 1, in which the residual error is sensedafter each stroke.

4. A method according to claim 1, in which the workpiece is supported ontwo spaced supports, and the straightening or bending strokes areapplied to the workpiece between the supports by a fluid-operated ram.

5. A method according to claim 1, in which the length of each stroke isdetermined by an automatic control system having an input from an errorsenser arranged to sense the residual error when the workpiece isunloaded, and an output connected to a ram for applying the bending orstraightening strokes, so as to control the length thereof, the controlsystem including a programming section arranged to apply one of twopreselected programs of increments to the output signal, depending uponwhether the sensed residual error is above or below the firstpreselected value.

6. Apparatus for straightening or applying controlled bending to anelongated workpiece, including a poweroperated ram, and means forcontrolling the ram includinga position senser for detecting theinstantaneous position or shape of the workpiece, and a computerincluding a programming section and an information storage section, anda differentiatorarranged to compare the input signal from the positionsenser with a first preselected value, and to operate the ram on a firstprogram of strokes with increasing amplitudes, until the input signalfrom the position senser reaches the said preselected value, and then tooperate the ram on a second program of strokes which increase withsmaller increments.

1. A method of straightening or applying controlled bending to anelongated workpiece, in which the workpiece is subjected to a bendingstroke which imparts to it a deformation beyond the desired final shape,this deformation as measured beyond the desired final shape beingapproximately equal to, or slightly greater than, the estimated maximumelastic deformation, aNd the workpiece is then unloaded and subjected toa series of bending strokes which impart progressively increasingdeformation according to a preselected programme to the workpiece, andthe residual error between the actual and desired shapes is sensed whenthe workpiece is unloaded between at least some of said strokes, andwhen the residual error falls below a first preselected value theworkpiece is subjected to a further series of strokes of smallerprogressive increments, according to another preselected program, andthe residual error is again sensed when the workpiece is unloadedbetween strokes, and when the final residual error falls below a secondpreselected value, the operation is terminated.
 1. A method ofstraightening or applying controlled bending to an elongated workpiece,in which the workpiece is subjected to a bending stroke which imparts toit a deformation beyond the desired final shape, this deformation asmeasured beyond the desired final shape being approximately equal to, orslightly greater than, the estimated maximum elastic deformation, aNdthe workpiece is then unloaded and subjected to a series of bendingstrokes which impart progressively increasing deformation according to apreselected programme to the workpiece, and the residual error betweenthe actual and desired shapes is sensed when the workpiece is unloadedbetween at least some of said strokes, and when the residual error fallsbelow a first preselected value the workpiece is subjected to a furtherseries of strokes of smaller progressive increments, according toanother preselected program, and the residual error is again sensed whenthe workpiece is unloaded between strokes, and when the final residualerror falls below a second preselected value, the operation isterminated.
 2. A method according to claim 1, in which the first seriesof strokes are of progressively increasing length, the increments beingof constant value, and the second series of strokes are also ofprogressively increasing length, with constant increments of smallervalue than the increments of the first series.
 3. A method according toclaim 1, in which the residual error is sensed after each stroke.
 4. Amethod according to claim 1, in which the workpiece is supported on twospaced supports, and the straightening or bending strokes are applied tothe workpiece between the supports by a fluid-operated ram.
 5. A methodaccording to claim 1, in which the length of each stroke is determinedby an automatic control system having an input from an error senserarranged to sense the residual error when the workpiece is unloaded, andan output connected to a ram for applying the bending or straighteningstrokes, so as to control the length thereof, the control systemincluding a programming section arranged to apply one of two preselectedprograms of increments to the output signal, depending upon whether thesensed residual error is above or below the first preselected value.